Radiation Detectors GAS-FILLED DETECTORGAS-FILLED DETECTORA gas-filled detector is used to detect incident radiation.EO 1.4 DESCRIBE the principles of operation of a gas-filleddetector to include:a. How the electric field affects ion pairsb. How gas amplification occursThe pulsed operation of the gas-filled detector illustrates the principles of basic radiationdetection. Gases are used in radiation detectors since their ionized particles can travel morefreely than those of a liquid or a solid. Typical gases used in detectors are argon and helium,although boron-triflouride is utilized when the detector is to be used to measure neutrons. Figure5 shows a schematic diagram of a gas-filled chamber with a central electrode.Figure 5 Schematic Diagram of a Gas-Filled DetectorThe central electrode, or anode, collects negative charges. The anode is insulated from thechamber walls and the cathode, which collects positive charges. A voltage is applied to theanode and the chamber walls. The resistor in the circuit is shunted by a capacitor in parallel, sothat the anode is at a positive voltage with respect to the detector wall. As a charged particlepasses through the gas-filled chamber, it ionizes some of the gas (air) along its path of travel.The positive anode attracts the electrons, or negative particles. The detector wall, or cathode,attracts the positive charges. The collection of these charges reduces the voltage across thecapacitor, causing a pulse across the resistor that is recorded by an electronic circuit. The voltageapplied to the anode and cathode determines the electric field and its strength.Rev. 0 Page 11 IC-06